Nailing strips, consisting of strips of nails bonded together in various ways are required for a large number of different industrial applications. In some cases they are used in nailing applicators in which a strip of nails is used in a straight magazine, the strip being formed with the nail shanks in a generally diagonal fashion, so that the nail heads of each nail overlap, and the nail shanks are close alongside one another. In other cases, nailing strips are used in drum magazines. In this case, the nailing strip is commonly formed with the nails parallel to one another with their heads spaced apart, so that the strip of nails may be wound into a relatively long coil, which is inserted into the drum.
In either case, various different systems have been used for joining the nails together. In some cases the nails are joined simply by adhesive paper, or adhesive plastic. In other cases the nails are held together by various forms of adhesive or glue, usually a hot melt type of adhesive. Usually nailing strips of this type are relatively speaking, inflexible and are only suitable for use in the type of nailing applicators having a straight magazine, and are not generally speaking, suitable for use in nailing applicators using a drum magazine.
There have been numerous attempts to provide nails which are formed into a strip by welding parallel lengths of wire to the nail shanks at spaced intervals. This has numerous apparent advantages over using paper or adhesive. Paper is torn easily and the nailing strip may become separated, causing machine down-time.
Nailing strips in which the nails are bonded together adhesively are relatively inflexible and are only suitable for nailing applicators having a straight magazine. In addition, such adhesively bonded nail strips must be handled carefully, since the strips are easily broken during shipping and handling. An additional disadvantage of this system is that the dried adhesive separates from the nail shank as it is driven in and accumulates around the work place. Unless the work location is cleaned at regular intervals the debris will collect and eventually cause an inconvenience.
Accordingly, the use of parallel wires to join nails into a strip has great advantages over other systems. In the past in fact, nail strips in which the nails are joined together with welded wires have achieved considerable popularity. There are however, known problems in relation to wire welded strips of nails. The wires must be relatively thin and flexible, so as to avoid difficulties in insertion of the nail and in the separation of the nail from the rest of the strip.
The wires make point to point contact with the individual nails, so that the actual contact area is quite small. The actual time during which current can flow from the welding machines to the wires and thus to the nails is thus restricted by the small area of contact between the wires and the nails themselves.
Such strips are formed automatically and the welding machines which are used to form the welds must be set to precise tolerances. If there is any tendency for the welding current to increase beyond a preset limit, the strip wires may be burned through at the location of the weld. On the other hand, if the welding current is too low, then the weld joint will be inadequate and the nail will become separated from the strip wire.
It is well known that the principle cause of this problem is the fact that as the wire to be used for making the nails is drawn through the typical drawing die, the die drawing compound forms a surface layer on the nail.
It is this surface layer which causes most of the difficulties to achieving a precise weld of the strip wire to the nail. The surface layer tends to obstruct the flow of electricity between the strip wire and the nails so that the welds are improperly formed.
It will of course be appreciated that the automatic welding machines must operate at high speed for economy. They contact the strip wire where it contacts the nail only for a fraction of a second, and any interference with the flow of current will tend to cause problems for the welding equipment and will result in failed welds. Increasing the current burns the strip wire and causes sparks to fly around the work place. The problem is particularly bad with coated nails such as zinc coated nails.
Cleaning away of the surface layer of the nail at the point of the weld seems, at first sight, to be an obvious solution to the problem. However, the various cleaning methods that are available, such as grinding, sanding, chemical treatment and the like produce inconsistent results, so that the welds are unpredictable.
Clearly, it is desirable to provide a system for removing the surface layer at the two locations where the strip wires will be welded, in a manner which leaves a clean, dry contact surface for producing perfect and consistent welds between the wires and the nails.